The present invention relates to a rolling bearing device with a sensor and relates to a strain sensor.
As a rolling bearing device with a sensor, there has conventionally been provided a double-row angular contact ball bearing device described in JP 2002-213438 A.
In this double-row angular contact ball bearing device, balls are placed between one of two-row raceway grooves formed in the inner circumferential surface of the outer ring and the raceway groove of the first inner ring, while balls are placed between the other of the two-row raceway grooves of the outer ring and the raceway groove of the second inner ring.
The first inner ring and the second inner ring are spaced from each other in an axial direction of the bearing device. In the outer circumference portion of the outer ring facing the portion between the first inner ring and the second inner ring, a groove having a generally trapezoidal cross section is formed so as to extend in the circumferential direction of the outer ring. A pressure sensor is placed at this groove. The lead wire of the pressure sensor is connected to a sensor output processing unit. The sensor output processing unit receives an output from the pressure sensor and, in a continuing series, measures a preload applied to the outer ring.
Based on an output of the sensor output processing unit, the conventional double-row angular contact ball bearing device described above adjusts the load applied to the outer ring so as to adjust the preload, which is applied to the outer ring to a proper value. The conventional double-row angular contact ball bearing device measures the preload after assembly of bearing component parts, thus having an advantage that there is no need for considering dimensional variation of each bearing component part.
However, the conventional double-row angular contact ball bearing device has a need for taking into consideration errors due to mounting accuracy of the pressure sensor. This poses a problem that adjustment of the instrumentation amplifier or the like is required based on the mounting accuracy of the pressure sensor.
Further, in the conventional double-row angular contact ball bearing device, since the sensor is a pressure sensor having a considerable thickness, it is necessary to deepen the depth of the groove in which the pressure sensor is to be housed. As a result, there is a problem that the cost for the formation of the groove is increased, resulting in a large mounting cost of the pressure sensor.
Moreover, since not only the pressure sensor described above but sensors for measurement of strain are conventionally high in cost for the sensors themselves, there is a problem that sensor-equipped rolling bearing devices with a sensor are high in manufacturing cost.